The following Patent document 1 discloses a battery assembly body that is configured in such a manner that plural batteries each having a rectangular parallelepiped shape and the positive pole and the negative pole of each adjoining pair of batteries are connected to each other in series by a busbar. Each of the batteries constituting the battery assembly body is formed with a gas vent (hereinafter referred to as a vent where appropriate) for venting gas that is generated inside the battery. For example, this vent is formed by forming an opening through a side wall of the battery and closing it by a thin metal film or the like. With this structure, gas that is generated inside the battery is discharged through the vent breaking the metal film when the pressure inside the battery has become higher than or equal to a prescribed value.
In this type of battery, usually, an electrode surface on which at least one of the positive pole and the negative pole is disposed is formed with a gas vent. For example, an electrode surface on which both of the positive pole and the negative pole are disposed is formed with a gas vent approximately at the middle between the two electrodes. A battery assembly body that is formed by arranging such batteries is provided with an insulating resin duct for guiding and ejecting gas that is discharged through each vent. This duct extends in the battery arrangement direction so as to cover the vents (also called pressure release valves) and is formed with a flow passage for gas that is discharged through each pressure release valve between itself and the electrode surfaces of the battery assembly body.
Incidentally, since gas that is discharged through the gas vent of each battery has a relatively high temperature, the duct may be deformed because of exposure to such high-temperature gas. FIG. 3(a) is a sectional view of a duct 52 that is attached to the electrode surface 51 of a battery assembly body 50. In FIG. 3(a), as for the battery assembly body 50, only the electrode surface 51 and their neighborhood are shown and the other portions are omitted. As seen from FIG. 3(a), gas 54 that is discharged through a gas vent 53 flows through the duct 52 in the direction indicated by an arrow and is ejected outward. On the other hand, as shown in FIG. 3(b), when the duct 52 is heated by the gas 54, its central portion in the longitudinal direction is deformed and warped upward (indicated by an arrow; in the direction that goes away from the electrode surface 51). In this case, gaps 55 may be formed between the duct 52 and the electrode surface 51 to cause leakage of part of the gas 54 through the gaps 55.
In this connection, Patent document 1 has a disclosure that plural batteries (battery assembly body) are housed and fixed in a case and the duct is covered with an insulating resin cover member from above and the cover member is held by the case with the duct pressed against the electrode surfaces. With this structure, the duct can be held between the cover member and the electrode surfaces of the battery assembly body and hence the deformation of the duct can be suppressed.